1. Field of the Invention
The present invention generally relates to a laser technique, in particular, to a laser apparatus with all optical-fiber, which is capable of emitting a green laser light with a high efficiency.
2. Description of Related Art
In recent years, as the laser projection concept has become prevailing, the demand on green laser light sources with small scale and high power is gradually increased, but green laser diodes are still immature. As for diode pumped solid state (DPSS) laser, the frequency-doubling green laser has problems about assembly difficulty and heat dissipation, and what's worse, the heat dissipation further affects the laser stability. As a result, it cannot achieve both the small scale feature and the desirable heat dissipation mechanism. However, a green gas laser has problems of low efficiency, large volume, and high price.
Currently, the realized wave bands of an optical-fiber laser are mostly close to infrared and middle infrared wave bands, and are widely applied to mechanical processing, biomedical, and communicating purposes. However, the optical-fiber laser in visible-light wave bands is still in the stage of being researched in the laboratory, and the total power thereof still cannot be distinctly improved.
In the prior art, in U.S. Pat. No. 5,638,394, a laser diode with a wavelength of 980 nm serving as a pumping light source emits lights to an optical fiber doped with both ytterbium (Yb) and terbium (Tb), and a blue reflecting mirror and a green reflecting mirror are placed on two ends of the optical fiber, so as to form a laser resonance cavity. The generated light is not in an all optical-fiber structure, so the stability thereof is rather poor. In addition, the optical-fiber laser doped with Tb also has a poor efficiency. In another U.S. Pat. No. 5,805,631, a laser diode with a wavelength from 790 nm to 900 nm serving as a pumping light source emits lights to an optical fiber doped with both praseodymium (Pr) and Yb, and a laser resonance cavity is formed on two ends of the optical fiber in a manner of reflecting mirrors or gratings. A single pumping light source is used, such that the Pr ion excited state absorption (ESA) effect cannot be sufficiently utilized.
As for the green lasers, the researching direction thereof is a laser system with a small size, high power, and high stability.